\begin{table}[H]\centering\small
\caption{The post-ChatGPT structural break. Columns 2--3: Q5$-$Q1 forward-return spread (\%/yr, Newey--West \textit{t}) in each sub-period. Column 4: coefficient on AI~$z$\,$\times$\,Post-2022 from a pooled OLS (size and momentum controls, year-clustered SE).}\label{tab:break}
\begin{tabular}{lccc}\toprule
& \multicolumn{2}{c}{Q5$-$Q1 spread} & Interaction \\
\cmidrule(lr){2-3}
Signal & Pre (2010--21) & Post (2022--24) & AI$\times$Post \\\midrule
AI adoption & +2.2 \tstat{2.04} & +14.3 \tstat{2.15} & +0.0199 \tstat{1.17} \\
AI infrastructure & +1.4 \tstat{0.91} & +13.6 \tstat{2.44} & +0.0277 \tstat{2.63} \\
AI composite & +2.5 \tstat{1.58} & +14.6 \tstat{2.07} & +0.0270 \tstat{1.78} \\
\bottomrule
\end{tabular}\end{table}